1. Field of the Invention
The present invention relates to a thermal recording head used in a recording system using thermal energy.
2. Related Background Art
Since a conventional recording system utilizing thermal energy is based on nonimpact recording, the noise level is very low in such a system. In addition, this system can perform color recording and thus has received a great deal of attention in recent years.
In the conventional recording system, recording information is transmitted as an electrical signal to a thermal recording head, i.e., electro-thermal conversion elements. In each electro-thermal conversion element, a heating resistor layer is formed on a substrate and at least a pair of electrodes are connected to the heating resistor layer. In this context, "substrate" means a carrier for the heating resistor layer. The substrate can be prepared by forming a proper layer on a support. Since the thermal recording head is generally compact, the heating resistor layer comprises a thin film, a thick film or a semiconductor film. In particular, since a thin film type resistor layer requires lower power consumption than other types and has good thermal response, a thin film is preferable as a constituting element of the thermal recording head, and its applications are increasing.
Good thermal response for a given electrical signal, high thermal conductivity, good heat resistance against self thermal dissipation, high durability against various factors (e.g., thermal history), etc. are required as properties of the heating resistor layer for a thermal recording head. Furthermore, when a thermal recording head is brought into contact with a heat-sensitive sheet or a thermal transfer ink ribbon, it must have a small friction coefficient.
None of the conventional heating resistor layers of thermal recording heads is completely satisfactory. There is much room for further improvements in the various properties of the heating resistor layer enumerated above.
In a conventional thermal recording head, an antiwear layer is formed on the surface of the heating resistor layer to improve the antiwear property. In this case, thermal response is often sacrificed.
In a conventional thermal recording head, when recording is performed on a recording medium such as a sheet with a rough surface, the thermal recording head must be brought into tight contact with the recording medium at a high pressure if characters must be recorded in complete dot shapes. The thermal recording head wear is therefore considerable. Demand has therefore arisen for further improvement in the antiwear properties of thermal recording heads.